Generation of SiO2 Interface States at Low Temperature with Ionizing Irradiation

Generation of SiO2/Si interface states at low temperature with ionizing irradiation has been a subject of much interest and study. Conventionally generation of interface states with ionizing irradiation is measured with a technique developed by Jenq. This technique has been primarily used to measure generation of interface states located within an 0.7 eV wide energy band centered about the intrinsic Fermi level. In this paper, a different technique is used to measure the generation of SiO2/Si interface states at low temperature following ionizing irradiation from a Co60 ¿ source. The technique used to measure changes in the interface state density is the double pulse CCD transfer inefficiency method. This method is more sensitive than the Jenq technique and measures interface states 0.1 to 0.2 eV from the valence or conduction band edges. Results from the present study reveal that Co60 ionizing radiation produce SiO2/Si interface states at low temperatures. These states are generated without the need for any room temperature anneals. Specifically, 1.2×1010 cm-2eV-1 interface states near the valence band edge were generated at low temperature following exposure to a 1×106 Rad(Si) dose. Annealing the CCDs at room temperature decreases the number of interface states by approximately 4×109states/cm2-eV.